Actual winners v expected winners explained

What are actual winners and expected winners?

Actual winners are the races a group of runners won. Expected winners are the number the odds implied, found by turning each runner's price into a probability and adding them up.

A horse at 3/1 has an implied chance of one in four, or 0.25. A horse at evens has 0.50 and a horse at 9/1 has 0.10. Add those chances across every runner a trainer saddled and you have the number of winners the market expected from that trainer.

A trainer whose runners are mostly favourites should win often

Racing records

Convert each runner's odds into an implied chance, add the chances to get expected winners, count the actual winners, then divide actual by expected.

The worked example uses ten runners from evens to 20/1. Their implied chances add up to 1.88 expected winners. If three of them won That looks exceptional, but ten runs prove nothing: one more winner or one fewer would move the figure hugely. The same calculation over 500 runners is far more telling.

Racing records

Above 1.00 they won more often than expected, and below 1.00 less often.

A trainer on 1.20 over several hundred runners has consistently beaten the market's expectations one on 0.80 has disappointed. Because starting prices carry a bookmaker margin, most large groups sit a little below 1.00, so a figure around 1.00 at starting price is already slightly better than average.

Racing records

Figures from the two sources should not be compared directly.

Betfair SP sits closer to a fair price. The win rate by odds data page includes a Betfair SP band table alongside starting price.

Racing records

With few winners, one result can swing the figure from well below 1.00 to well above it.

A useful rule is to look at the number of winners rather than runs. Ten winners is too few to judge, thirty starts to show a pattern and fifty or more gives real confidence. Groups built from big-priced runners need even more, because each winner moves the figure a long way.

• Under 10 winners: treat as noise
• 10 to 30 winners: a hint worth watching
• 30 to 50 winners: a pattern forming
• 50 or more winners: worth relying on
• Check the pattern holds season by season

Racing records

Strike rate shows how often a group wins

The chart on this page shows the idea at market level: it compares the actual win rate at each starting price with the chance implied by the price. The strike rate guide explains the other half of the picture.

The same logic applies to angles and systems.

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